Recordset2.LockEdits Property (DAO)

Sets or returns a value indicating the type of locking that is in effect while editing.

Syntax

expression .LockEdits

expression A variable that represents a Recordset2 object.

Remarks

The setting or return value indicates the type of locking, as specified in the following table.

Value	Description
True	Default. Pessimistic locking is in effect. The page containing the record you're editing is locked as soon as you call the Edit method.
False	Optimistic locking is in effect for editing. The page containing the record is not locked until the Update method is executed.

You can use the LockEdits property with updatable Recordset objects.

If a page is locked, no other user can edit records on the same page. If you set LockEdits to True and another user already has the page locked, an error occurs when you use the Edit method. Other users can read data from locked pages.

If you set the LockEdits property to False and later use the Update method while another user has the page locked, an error occurs. To see the changes made to your record by another user, use the Move method with 0 as the argument; however, if you do this, you will lose your changes.

When working with Microsoft Access database engine-connected ODBC data sources, the LockEdits property is always set to False, or optimistic locking. The Microsoft Access database engine has no control over the locking mechanisms used in external database servers.

Note

You can preset the value of LockEdits when you first open the Recordset by setting the lockedits argument of the OpenRecordset method. Setting the lockedits argument to dbPessimistic will set the LockEdits property to True, and setting lockedits to any other value will set the LockEdits property to False.

Example

This example demonstrates pessimistic locking by setting the LockEdits property to True, and then demonstrates optimistic locking by setting the LockEdits property to False. It also demonstrates what kind of error handling is required in a multiuser database environment in order to modify a field. The PessimisticLock and OptimisticLock functions are required for this procedure to run.

Sub LockEditsX() 
 
 Dim dbsNorthwind As Database 
 Dim rstCustomers As Recordset2 
 Dim strOldName As String 
 
 Set dbsNorthwind = OpenDatabase("Northwind.mdb") 
 Set rstCustomers = _ 
 dbsNorthwind.OpenRecordset("Customers", _ 
 dbOpenDynaset) 
 
 With rstCustomers 
 ' Store original data. 
 strOldName = !CompanyName 
 
 If MsgBox("Pessimistic locking demonstration...", _ 
 vbOKCancel) = vbOK Then 
 
 ' Attempt to modify data with pessimistic locking 
 ' in effect. 
 If PessimisticLock(rstCustomers, !CompanyName, _ 
 "Acme Foods") Then 
 MsgBox "Record successfully edited." 
 
 ' Restore original data... 
 .Edit 
 !CompanyName = strOldName 
 .Update 
 End If 
 
 End If 
 
 If MsgBox("Optimistic locking demonstration...", _ 
 vbOKCancel) = vbOK Then 
 
 ' Attempt to modify data with optimistic locking 
 ' in effect. 
 If OptimisticLock(rstCustomers, !CompanyName, _ 
 "Acme Foods") Then 
 MsgBox "Record successfully edited." 
 
 ' Restore original data... 
 .Edit 
 !CompanyName = strOldName 
 .Update 
 End If 
 
 End If 
 
 .Close 
 End With 
 
 dbsNorthwind.Close 
 
End Sub 
 
Function PessimisticLock(rstTemp As Recordset2, _ 
 fldTemp As Field, strNew As String) As Boolean 
 
 dim ErrLoop as Error 
 
 PessimisticLock = True 
 
 With rstTemp 
 .LockEdits = True 
 
 ' When you set LockEdits to True, you trap for errors 
 ' when you call the Edit method. 
 On Error GoTo Err_Lock 
 .Edit 
 On Error GoTo 0 
 
 ' If the Edit is still in progress, then no errors 
 ' were triggered; you may modify the data. 
 If .EditMode = dbEditInProgress Then 
 fldTemp = strNew 
 .Update 
 .Bookmark = .LastModified 
 Else 
 ' Retrieve current record to see changes made by 
 ' other user. 
 .Move 0 
 End If 
 
 End With 
 
 Exit Function 
 
Err_Lock: 
 
 If DBEngine.Errors.Count > 0 Then 
 ' Enumerate the Errors collection. 
 For Each errLoop In DBEngine.Errors 
 MsgBox "Error number: " & errLoop.Number & _ 
 vbCr & errLoop.Description 
 Next errLoop 
 PessimisticLock = False 
 End If 
 
 Resume Next 
 
End Function 
 
Function OptimisticLock(rstTemp As Recordset, _ 
 fldTemp As Field, strNew As String) As Boolean 
 
 dim ErrLoop as Error 
 
 OptimisticLock = True 
 
 With rstTemp 
 .LockEdits = False 
 .Edit 
 fldTemp = strNew 
 
 ' When you set LockEdits to False, you trap for errors 
 ' when you call the Update method. 
 On Error GoTo Err_Lock 
 .Update 
 On Error GoTo 0 
 
 ' If there is no Edit in progress, then no errors were 
 ' triggered; you may modify the data. 
 If .EditMode = dbEditNone Then 
 ' Move current record pointer to the most recently 
 ' modified record. 
 .Bookmark = .LastModified 
 Else 
 .CancelUpdate 
 ' Retrieve current record to see changes made by 
 ' other user. 
 .Move 0 
 End If 
 
 End With 
 
 Exit Function 
 
Err_Lock: 
 
 If DBEngine.Errors.Count > 0 Then 
 ' Enumerate the Errors collection. 
 For Each errLoop In DBEngine.Errors 
 MsgBox "Error number: " & errLoop.Number & _ 
 vbCr & errLoop.Description 
 Next errLoop 
 OptimisticLock = False 
 End If 
 
 Resume Next 
 
End Function